Wire size for shed

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Old 04-30-13, 11:31 AM
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Wire size for shed

I'm building a shed behind my house and was wondering what gauge size wiring i should use. Total length will be about 120 feet. I want to have a 20 amp receptacle outside the shed (for garden tools) and a light inside the shed. From what i read 20 amps require 12 gauge wire but my run is about 120 feet from the breaker box in the garage to the shed. Should i use 10 gauge or 12 is enough?

Also not sure if this makes a different but 60 feet will running under the house (crawlspace) and the other 60 feet under ground (about 2 feet) enclosed inside a pvc pipe.
 
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Old 04-30-13, 11:51 AM
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12-2 UF should be okay but if you want to bump it up to 10-2 you can.
 
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Old 04-30-13, 12:30 PM
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If you are going to be using type UF (underground feeder) cable then don't bother with the PVC conduit (not pipe) except where the cable comes up from the ground. Pulling type UF through conduit will teach you many new "bad" words.
 
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Old 04-30-13, 08:44 PM
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From what i read 20 amps require 12 gauge wire but my run is about 120 feet from the breaker box in the garage to the shed. Should i use 10 gauge or 12 is enough?
#12 can supply up to 8 amps of load at 120V and 120 feet with 3% or less voltage drop. #10 will get you up to 14 amps; above that you'll need #8.

Just a quick calculation using whole, even numbers for the loads.
 

Last edited by Nashkat1; 05-03-13 at 03:37 PM. Reason: typos
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Old 05-03-13, 11:35 AM
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Thanks I think ill go with #10 inside a conduit PVC to be safe..I can still use 20 am receptacles with 10-2 correct?
 
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Old 05-03-13, 12:43 PM
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I can still use 20 am receptacles with 10-2 correct?
Yes. Code requires a disconnect. Simplest would be to use one side of a 30 amp (or larger) unfused AC disconnect* where the wiring enters and transition to 12-2 NM-b (Romex) in the AC disconnect housing. First receptacle must be GFCI and the others non GFCI receptacles from the load side of the first receptacle.

*You could use a single pole 20 amp "light" switch but you would probably have trouble connecting the #10 without first pigtailing on #12 unless you used a commercial side or back wired switch plus you would need to buy a box. The AC disconnect provides the box and a switch designed for #10 wire all in one unit for probably less cost. You just wire nut the neutrals and wire the blacks to one side of the switch. (The other pole of the switch isn't used.)
 
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Old 05-03-13, 03:41 PM
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*You could use a single pole 20 amp "light" switch but you would probably have trouble connecting the #10 without first pigtailing on #12 unless you used a commercial side or back wired switch
I've done it. It's a bit stiff but it'll fit. You can use either the bending holes in most wire strippers or a pair of needle-nose pliers to shape the end of the wire.
 
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